The overall objective of this study is to investigate the incidence, severity and etiology of chronobiological dysfunction (including sleep/wake disorders) in the blind, and develop a rational approach to therapy. We plan to follow up a previous pilot survey of blind subjects with a detailed questionnaire survey, sleep recordings, solid state ambulatory monitoring in the home environment, studies in a time isolation facility, 48 hour blood withdrawal studies of hormonal and metabolic rhythms, and development and implementation of a time-oriented computerized clinical data base and system of analysis.